Enhance Asynchronous Performance of SHJ Implementation

[metesynnada]

Is your feature request related to a problem or challenge?

The current SymmetricHashJoin (SHJ) operator could benefit from improved handling of the pending state, enhancing overall async performance.

Describe the solution you'd like

To optimize the asynchronous performance of the SymmetricHashJoinoperator, we propose merging the two child streams using futures::select. This will enable simultaneous polling of both streams and execute the branch corresponding to the future that completes first.

Describe alternatives you've considered

NA

Additional context

NA